The present invention relates to prosthetic cardiac valves for replacement of diseased aorta valves or use in mechanical hearts.
The earliest prosthetic aortic and mitral heart valves used clinically were the ball-in-cage design, similar in design to standard check valves used with other fluids and having an attaching ring for sewing the valve into position in the patient's heart. These particular valves have been successfully used for many years. However, the disadvantages of this type of valve led to research in design of other types of valves. Two of the main disadvantages were that the relationship of a sphere or ball to the main ring diameter impeded the blood flow by the ball within the artery restricting the orifice size that could be obtained and also the disadvantages of having the cage to impede the flow of the blood. That is to say the ball has to have a diameter of between 30 and 35 percent greater than the ring to avoid impaction and in the case of a mitral valve the small ventricle which often accompanies mixed lesion of mitral incompetence and mitral stenosis, or pure calcified stenosis, the cage makes physical contact with the myocardium. This traumatizes the myocardium and contact with the interventricular septum may trigger off ectopic beats, resulting in arrhythmia which may lead to fatal ventricular fibrillation. Physical contact of the cage with the myocardium may cause the cage to lever off the sutureline which attempts to overcome this fault by selecting a smaller prosthesis may result in an excessive pressure gradient across the prosthesis.
Also in patients with a mixed valvular lesion of aortic incompetence and stenosis, or pure calcified stenosis the small annulus creates a need for a prosthetic device with an improved blood flow past the check element of the valve and with less obstruction by the cage. In order to overcome the problems with the ball-in-cage type heart valve, one of the valves developed provided a ring for attaching a sewing ring and seat for the check valve and having one or two arm extending from one or both sides of the ring with each arm having a small ring on the end thereof which bends and to be centered on the axes passing through the center of the ring and having an extension or protrusion extending through the small ring at the end of the arm for guiding the check elements in an opening an closing and to limit its movement when opening, the mitral valve having one arm extending on one side while the aorta valve having a pair of arms, one extending on either side of the main ring. The mitral valve is a generally lenticular shaped poppet element having a T-shaped protrusion extending from the center thereof through the main ring and hooked into the smaller ring with the cross or transverse portion of the T preventing the check element from escaping and limiting its movement, while the aorta check member has a protrusion from either end passing through the small rings on the end of each arm for guiding check member and limiting its movement. The check member in the aorta has a portion of a sphere less than a hemisphere for seating in the main ring and seat and a truncated cone connected to the other side. These advanced type of heart valves have generally been hand fashioned for experimental testing and the present invention relates to a method for manufacturing these advanced valves in larger quantities while reducing the overall cost and maintaining the high standards of quality necessary in a prosthetic cardiac valve.
Other types of valves for use in replacing diseased mitral and aortic valves have also been suggested in the past. For instance, it has been suggested to use various types of flaps hinged or held in various ways and adapted for flapping open and closed. These types of valves however have not been generally robust or sufficiently sturdy for more generalized use. It has also been suggested to make a toroidal check element heart valve as well as a valve formed of a resilient spirals of conical shape which are held on the annular base and overlap each other so as to form a sealed cone blockage in one direction of blood flow and angular openings in the other direction of blood flow.
Typical prior art heart valve can be seen in the following U.S. Patents:
______________________________________ U.S. PAT. NO.: INVENTOR ______________________________________ 3,601,877 C. C. GOOSEN 3,538,514 G. SCHIMERT, ET AL. 4,021,863 A. WOIEN 4,319,364 R. L. KASTER 3,825,956 F. W. CHILD 3,959,827 R. L. KASTER 4,197,593 R. L. KASTER ______________________________________